/Engine/Source/Editor/UnrealEd/Public/FileHelpers.h
Looks at all currently loaded packages and saves them if their "bDirty" flag is set and they include specified clasees, optionally prompting the user to select which packages to save)
true on success, false on fail.
static bool SaveDirtyContentPackages ( [TArray](API\Runtime\Core\Containers\TArray)< [UClass](API\Runtime\CoreUObject\UObject\UClass) * > & SaveContentClasses, const bool bPromptUserToSave, const bool bFastSave, const bool bNotifyNoPackagesSaved, const bool bCanBeDeclined )